Pushbutton switch

ABSTRACT

A momentary pushbutton electric switch featuring an elongated plunger, contained in a casing, and having one or more longitudinally extended grooves, cut more deeply into the plunger at the lower end, and tapering outward at the top of the groove, the floor of the groove providing a cam surface. In one or more of the grooves rides an inner terminal, while an outer terminal lies across and outside the same groove, both terminals extending upward from the bottom of the casing. The plunger is biased upwardly and outwardly of the casing by a spring, and when the plunger is in its upward, inoperative position, the inner terminal lies in the deeper part of the groove and the outer terminal is thus prevented from contacting it. When the plunger is depressed against the upward bias of the spring to its operative position, the inner terminal rides against the cam surface and is forced outwardly of the groove toward the circumference of the plunger until it contacts the outer terminal. The casing may be assembled in either of two ways, one way providing an upright pushbutton, the other providing a pushbutton tilted at an angle to the supporting surface.

llnite tates int [72] inventors Charles Azel Barney Stow; Julian Joseph Bishop, Jun, Belmont, both oil Mass.

[21] Appl. No. 358

[22] Filed Jan. 2, 1970 [45] Patented Dec. 7, 11971 [73] Assignee Ark-Les Switch Corporation Watertown, Mass.

[54] PUSHBU'ITON SWITCH 5 Claims, 11 Drawing Figs.

[52] 11.8. C1 200/159 A, 200/153 LA, 200/168 R, 200/168 E [51] 1nt.C1 ll-101li3l12, H0111 3/14 [50] Field 0t Search 200/159,

153 LA, 168 A, 159A, 166 BC, 168E 2,877,323 3/1959 Nahev 3,183,333 5/1965 G0lbeck....

ZOO/159 200/159 ABSTRACT: A momentary pushbutton electric switch featuring an elongated plunger, contained in a casing, and having one or more longitudinally extended grooves, cut more deeply into the plunger at the lower end, and tapering outward at the top of the groove, the floor of the groove providing a cam surface. ln one or more of the grooves rides an inner terminal, while an outer terminal lies across and outside the same groove, both terminals extending upward from the bottom of the casing. The plunger is biased upwardly and outwardly of the casing by a spring, and when the plunger is in its upward, inoperative position, the inner terminal lies in the deeper part of the groove and the outer terminal is thus prevented from contacting it. When the plunger is depressed against the upward bias of the spring to its operative position, the inner terminal rides against the cam surface and is forced outwardly of the groove toward the circumference of the plunger until it contacts the outer terminal. The casing may be assembled in either of two ways, one way providing an upright pushbutton, the other providing a pushbutton tilted at an angle to the supporting surface.

PATENTEU DEC 7 I97! SHEET 3 [1F 4 FIG 9 agemls l PATENTEU um Han SHEET 0F 4 FIG 8 PUSHBUTTON swircii This invention relates to electrical switches. More particularly, it relates to a momentary pushbutton switch for maintaining electrical contact only while the pushbutton is depressed, especially useful in a keyboard.

In repeated use of a pushbutton electric switch, as in a keyboard, the terminals must be continuously moved into and out of contact, with resulting stress and wear on the terminals, which eventually break, rendering the switch inoperable.

It is an object of this invention to provide a momentary pushbutton electric switch in which stress and wear on the terminals is minimized, with resulting increase in the durability and useful life of the switch.

It is a further object of this invention to provide a momentary electric switch that is simple, inexpensive and reliable and especially adapted for use in a keyboard configuration.

The invention features an elongated plunger, contained in a casing, with one movable and one fixed terminal both extending upward from the bottom of the casing. The plunger has one or more longitudinally extended grooves, cut more deeply into the plunger at the lower end, and tapering outward at the top of the groove. The floor of the groove providing a cam surface. In one or more of the grooves rides an inner terminal, while an outer terminal lies across and outside the same groove. The plunger is biased upwardly and outwardly of the casing by a spring, and when the plunger is in its upward, inoperative position, the inner terminal lies in the deeper part of the groove and the outer terminal is thus prevented from contacting it. When the plunger is depressed against the upward bias of the spring to its operative position, the inner terminal rides against the cam surface and is forced outwardly of the groove toward the circumference of the plunger relatively to the outer terminal. The contact or lack of contact thus established is continued as long as the plunger is kept in a depressed position. The invention further features a base comprising two parts having surfaces that are contiguous when the casing is assembled; each surface is inclined at a predetermined angle, for example, each at an angle of to the opposite surface of the same part, and the two parts may be combined either with the inclinations cumulative, to tilt the upper part of the casing (and the pushbutton cap) at an angle of to the supporting surfaces, as is desirable for keyboard use, or cancelling, so that the entire casing is normal to the supporting surface, so that alternative inclinations are provided up to the sum of said predetermined angles.

Although the terminal flexes over its entire length, the chief wear and fatigue of the material occurs at the point at which it is secured to the base or support. The stress and fatigue at this flexion point is partly a function of the length of the terminal; thus a short terminal must flex more sharply at the flexion point to achieve the same displacement at the outer end that may be achieved by a longer terminal with less flexion at this point. Providing longer terminals tends to obviate this stress at the flexion point; however, increasing the terminal length also introduces the further problem that, because of bending over the greater length of the terminals, the relative positions of their outer ends cannot be accurately defined. The pushbutton assembly of the present invention meets this difficulty by biasing both terminals inwardly against the traveling portion of the plunger, thus providing improved control of the outer contacting portions of the terminals while retaining the advantages of the increased length.

Because of the elongated shape of the plunger, the inner terminal remains at all times within a long groove, so that as the plunger is depressed and released, the inner terminal is not subjected to any abrupt displacements, but rather moves smoothly and continuously through a range of positions including the position in which it contacts or disconnects the outer terminal. As a result, the stress on the inner terminal that would result from such abrupt displacements is eliminated, and the lifetime of the inner terminal is extended, with consequent increased durability of the pushbutton switch.

Other objects, features and advantages will appear from the following description of a preferred embodiment of the invention, taken together with the attached drawings thereof, in which:

FIGS. 1 and 2 show two views of the assembled pushbutton attached to a supporting surface;

FIG. 3 shows an exploded view of the pushbutton assembly;

FIGS. 4, 5, 6 and 7 show perspective views of the plunger, case, base and receptacle;

FIG. 8 is a section taken along line 8-8 of FIG. 6;

FIG. 9 shows a detailed sectional view of the plunger, taken along line 99 of FIG. 4;

FIG. 10 is a view of the assembled pushbutton, the case being cut away to show a perspective view of the plunger; and

FIG. II shows a section ofthe plunger taken along line 31-- ill of FIG. 9.

Referring now to the drawings and particularly to FIGS. 1!, 2 and 3, the assembly comprises a plunger 10 with detachable top 200 and cap 202, a casing 70, composed of a case 71, a base 72, and a receptacle 74, a spring 100, and an inner terminal 50, and outer terminal 54, and two connecting terminals 204 and 206.

Referring to FIG. 9, plunger 10 has a cap end l2, adapted to be attached to top 200, and is divided generally into a sliding section 16 of generally circular cross section, a generally cylindrical lower part 18 of outer diameter smaller than the diameter of sliding section 16, tapered in portion 20 toward end 22, and a projection 26 of generally square cross section, between sliding section l6 and lower part l8.

Spring has a top 102 and a bottom I04, and generally encircles the lower part 18 of plunger 10, and also encircles inner terminal 50 and outer terminal 54.

Case 71 has a neck 76 of circular cross section, of inner diameter adapted to permit sliding section 16 of plunger 10 to slide through it; it has four flat sides M of dimensions adapted to enclose projection 26 and of inside length to accommodate barrel section 18 when plunger I0 is depressed; the four flat sides 81 are joined to neck 76 by a shoulder 78. Each flat side 81 of case 71 has an inner surface 82 and a wedge-shaped bottom surface 83; a groove 84 is cut into each surface 82 near bottom 83, and surface 82 is beveled outwardly below groove 84.

Projection 26 of plunger 10 has a flat upper surface 27 with four corners 28, each corner 28 being beveled along inner surface 29 towards the generally annular flat inner surface 38. Top 102 of spring 100 seats against surface 30, thereby biasing plunger 10 upwardly within casing 70. Upper surface 27 seats against the inner surface of shoulder 78 when plunger 10 is released, thus limiting the upward motion of plunger 10.

Plunger 10 has four slots 32, extending from end 22 generally parallel to the long axis of plunger I0; each slot 32 is closed at its upper end 34, and has within it a cam surface 36, slanting generally upwardly and outwardly of slot 32. Below cam surface 36 is a rest surface 38, generally parallel to the long axis of plunger 10; below surface 38 is a section 40 tapering towards bottom 22 of plunger llIl). Each slot 32 opens through a corner 28 of projection 26.

Inner terminal 50 extends generally parallel to the long axis of plunger 10; it is biased inwardly towards plunger 10, and is adapted to ride within one groove 32; and has a bent bearing end 52 adapted to bear against cam surface 36 when plunger 10 is depressed, or against rest section 38 when plunger 10 is released, a horizontal section 51, and a stem 60. Outer terminal 54 has a similar horizontal section 53, a similar stem 62, an upper stem 56 extending generally parallel to inner terminal 50 and biased inwardly toward the plunger, and a contact section 58, extending at an angle to stem 56 across and outside the groove 32 in which inner terminal 50 rides.

Base 72 is of generally square cross section, and is divided generally into an upper part and a lower part 120, upper part 110 having outer dimensions to fit within the inner sides 82 of square sides 81 of case 71, and having in particular four rounded outer ridges I12 adapted to fit within grooves 84.

Upper part 110 has an upper surface 113 with four corner teeth 1 14 projecting upwardly therefrom. Lower part 120 has outer surfaces 122 of dimensions to match those of outer surface 81 of case 71 and has a bottom surface 124 slanted at an angle of 5 to the normal to the long axis of plunger 10. Base 72 has two holes 126 and 128 through it, terminating at upper surface 113 within slots 130 and 132. FIG. 8 shows a cross section of either of slots 130 and 132. Dimension L is slightly smaller than thickness of terminal 50 or 54.

Lower part 120 additionally provides base element positioning means comprising two orientation elements in the form of two square bosses 127 located at 180 from each other, and an attaching element in the form of a round locking section 129 carrying a rounded ridge 131 uniformly spaced from the bottom edge of surface 122.

Receptacle 74 has four outer sides generally at right angles to one another, including a shortest side 220 that is generally rectangular, a tallest side 222 also generally rectangular, and two connecting sides 140, having two parallel and two nonparallel edges. The cross-sectional size of receptacle 74 is adapted to match the dimensions of surfaces 81 of case 71. Bottom surface 142 lies in the plane of supporting surface 144 (as seen in FIGS. 1 and 2) while upper surface 146 is inclined at about 5 to surface 142.

Receptacle 74 provides receptacle positioning means.

A generally circular wall 214 is cut into top surface 146, and elongated into orientation element receiving means in the form of two positioning slots 210 and 212, located at tallest side 222 and shortest side 220 respectively, and of dimensions to accommodate bosses 127 of base 72. Attachment element receiving means is provided in the form of an annular groove 216 cut into wall 214 at a constant distance below surface 146. Wall 214 surrounds a generally circular floor 217, lying parallel to bottom surface 142. Through the center of receptacle 74 is a hole 218, countersunk at floor 217. A trench 219 is cut into floor 217, and connects with shafts 230 and 228, the intersection of trench 219 and shaft 228 forming a T" as seen in FIG. 7, and similarly with shaft 230. A second trench 221 similarly connects with two similar shafts (not shown).

Connecting terminal 204 is generally planar, and is bent at 249 to form a stern 250, having edge teeth 251 below bend 249, and a leaf 252, whose tip 253 bends downwardly.

To assemble the pushbutton, plunger 10 is first passed upwardly through case 71, cap end 12 foremost, until surface 27 of plunger 10 seats against the inner surface of shoulder 78 of case 71. Detachable top 200 and cap 202 are then attached to plunger 10. Spring 100 is then placed around section 18 of plunger 10, sliding past beveled surface 29 until top 102 of spring 100 seats against surface 30 of plunger 10. Inner terminal 50 is dropped into base 72 from above so that its horizontal section 51 lies in slot 130 while stem 60 extends downwardly through hole 126. Terminal 50 may be snapped into place in slot 130 which may then be sealed by ultrasonic welding means. Outer terminal 54 is similarly sealed into slot 132 and hole 128.

Base 72 is next attached to case 71. In assembly, outer terminal 54 slides upwardly past tapered portion 20 of plunger 10 to rest against cylindrical part 18, and similarly inner terminal 50 slides upwardly past tapering section 40 within slot 32 to rest against rest surface 38. When assembled, inner terminal 50 lies within one of slots 32 in plunger 10, and end 58 of outer terminal 54 lies across and outside the same groove. Ridges 112 on base 72 are snapped into grooves 84 within case 71 and wedge projections 83 may then be ultrasonically welded to the top surface of lower part 120 of base 70. When this has been accomplished, the outer surfaces 81 of case 71 and surfaces 122 of base 72 lie generally coplanar with one another, forming a generally smooth outer surface for this part of casing 70.

Connecting terminal 204 is then pressed downwardly into shaft 228 through receptacle 74, so that leaf 252 lies within trench 219 and tip 253 projects slightly downwardly into shaft 230 at the opposite end of trench 219. Edge teeth 251 bite into the walls of shaft 228 and serve to attach terminal 204 firmly to receptacle 74. A second connecting terminal 206 is similarly attached within trench 221. By means of nut 500 and screw 502, receptacle 74 is now attached to supporting surface 144.

Finally, base 72 is joined to receptacle 74; this may be done in either of two modes. In one mode, the 5 inclination of surface 124 of base 72 adds to that of top surface 146 of receptacle 74, so that top surface 113 of base 72 makes an angle of 10 with supporting surface 144, while in the second mode, the inclinations of base and receptacle cancel each other, so that top surface 113 lies generally parallel to the plane of supporting surface 144.

Ridge 131 of base 72 is snapped into annular groove 216 of receptacle 74, and bosses 127 fit within positioning slots 212 and 210. Stern 60 of inner terminal 50 extends into shaft 230, and top 253 presses firmly against stem 60, insuring a good electrical connection. Outer terminal 54 is similarly connected with connecting terminal 206.

In operation, when plunger 10 is depressed by pressure on cap 202, sliding section 16 of plunger 10 slides downwardly through neck 76 of case 71, and spring is compressed between surface 30 of plunger 10 and surface 113 of base 72. The downward displacement of plunger 10 is limited by surface 113 of base 72. Inner terminal 50, whose bearing end 52 in the outward or rest position of plunger 10 bears against surface 38 within a slot 32, now bears against cam surface 36 and is constrained to move outwardly until it touches and lifts and wipes against contact section 58 of outer terminal 54, thus completing the electric circuit. When plunger 10 is released, spring 100 is thereby released and causes plunger 10 to return to its initial position, its upward displacement being stopped when upper surface 27 seats against the inner surface of shoulder 78 of case 71. Inner terminal 50, again bearing against rest surface 38 of plunger 10, is now out of contact with outer terminal 54, and the circuit is broken.

What is claimed is:

1. In a momentary pushbutton switch having an open-ended housing with a base at the opposite end thereof, an axial plunger with an outer surface slideably mounted for reciprocating movement within said housing having its bottom end adjacent said base and its opposite top end extending outwardly from said housing for manual actuation thereof by movement toward said base into operative position and spring means normally maintaining said plunger in outwardly extended inoperative position,

that improvement which consists of an axially extended groove in said plunger having sides and a bottom actuating surface including a rest surface extending from a substantial distance from said bottom end and a cam surface sloping contiguously from the end of said rest surface remote from said bottom end toward said outer surface at an acute angle to the axis of said plunger, and

a pair of axially extended terminal elements mounted in said base and extending upwardly away therefrom and into contact with said plunger for operation thereby, said terminal elements comprising an inner terminal element positioned within said groove in inoperative position of said plunger and having its remote end portion in contact with the bottom of said groove for operation by said cam surface, and

an outer terminal element positioned outside of said groove and having its remote end portion extending thereacross and in contact with said plunger positively to maintain it out of contact with said inner terminal in inoperative position of said plunger whereby movement of said plunger toward said base moves said inner terminal by contact of its remote end portion with said groove cam surface relatively to said outer terminal and into contact therewith.

2. In a momentary pushbutton switch as claimed in claim 1, wherein said housing has a removable base, and said plunger has a conical outer surface at said bottom 'end for assembly of said outer terminal, and said rest surface has a sloped end tapering inwardly toward said bottom end for assembly of said inner terminal upon introduction of said case carrying said terminals into assembled position.

3. in a momentary pushbutton switch as claimed in claim 2,

wherein said plunger has a stop within said housing and said housing has an overlying cooperative stop limiting outward displacement of said plunger when biased by said spring means.

i. in a momentary pushbutton switch as claimed in claim ll wherein said sidewalls of said groove limits lateral movement of said inner terminal element.

5. In a momentary pushbutton switch having an open-ended housing with a base at the opposite end thereof, an axial plunger with an outer surface slidably mounted for reciprocating movement within said housing having its bottom end adjacent said base and its opposite top end extending from said housing for manual actuation thereof by movement toward said base into operative position and spring means normally maintaining said plunger in outwardly extended inoperative position,

that improvement which consists of a removable housing base means for mounting said switch alternatively in one of two differently inclined positions, said removable housing base means comprising a receptacle element including a pair of axially extended terminal elements mounted on said base and extending upwardly away therefrom for operation by said plunger, said receptacle element having positioning means inclined at a predetermined angle relatively to a plane perpendicular to said axis, and

a housing base element, including a pair of terminals, having cooperating positioning means inclined at said predetermined angle,

said base element cooperative positioning means comprising an attaching element and at least two orientation elements, and said receptacle positioning means comprising attachment element retaining means and at least two orientation element receiving means,

said orientation element receiving means being adapted to receive said orientation elements in either of said differently inclined positions, thereby providing alternative inclination of said housing relatively to said receptacle element up to twice said predetermined angle,

said terminals of said receptacle and housing base elements being in contact in said alternative inclinations,

and an axially extended groove in said plunger having sides and a bottom-actuating surface including a rest surface extending for a substantial distance from said bottom end, said rest surface having a sloped end tapering inwardly toward said bottom end. and a cam surface sloping contiguously from the end of said rest surface remote from said bottom end toward said outer surface at an acute angle to the axis of said plunger, said plunger having a downwardly tapering conical outer surface at said bottom end, and having a stop within said housing, said housing having an overlying cooperating stop limiting outward displacement of said plunger when biased by said spring means,

said axially extended terminal elements comprising an inner terminal element positioned within said groove in operative position of said plunger and having its remote end portion in contact with the bottom of said groove and an outer terminal element positioned outside of said groove and extending thereacross positively to maintain it out of contact with said inner terminal in inoperative position of said plunger,

said inner terminal sliding upwardly past said sloped end of said rest surface, and said outer terminal sliding upwardly past said conical outer surface upon introduction of said removable base means into assembled position, whereby movement of said plunger toward said base moves said inner terminal by contact of its remote end portion with said groove cam surface relatively to said outer terminal. 

1. In a momentary pushbutton switch having an open-ended housing with a base at the opposite end thereof, an axial plunger with an outer surface slideably mounted for reciprocating movement within said housing having its bottom end adjacent said base and its opposite top end extending outwardly from said housing for manual actuation thereof by movement toward said base into operative position and spring means normally maintaining said plunger in outwardly extended inoperative position, that improvement which consists of an axially extended groove in said plunger having sides and a bottom actuating surface including a rest surface extending from a substantial distance from said bottom end and a cam surface sloping contiguously from the end of said rest surface remote from said bottom end toward said outer surface at an acute angle to the axis of said plunger, and a pair of axially extended terminal elements mounted in said base and extending upwardly away therefrom and into contact with said plunger for operation thereby, said terminal elements comprising an inner terminal element positioned within said groove in inoperative position of said plunger and having its remote end portion in contact with the bottom of said groove for operation by said cam surface, and an outer terminal element positioned outside of said groove and having its remote end portion extending thereacross and in contact with said plunger positively to maintain it out of contact with said inner terminal in inoperative position of said plunger whereby movement of said plunger toward said base moves said inner terminal by contact of its remote end portion with said groove cam surface relatively to said outer terminal and into contact therewith.
 2. In a momentary pushbutton switch as claimed in claim 1, wherein said housing has a removable base, and said plunger has a conical outer surface at said bottom end for assembly of said outer terminal, and said rest surface has a sloped end tapering inwardly toward said bottom end for assembly of said inner terminal upon introduction of said case carrying said terminals into assembled position.
 3. In a momentary pushbutton switch as claimed in claim 2, wherein said plunger has a stop within said housing and said housing has an overlying cooperative stop limiting outward displacement of said plunger when biased by said spring means.
 4. In a momentary pushbutton switch as claimed in claim 1 wherein said sidewalls of said groove limits lateral movement of said inner terminal element.
 5. In a momentary pushbutton switch having an open-ended housing with a base at the opposite end thereof, an axial plunger with an outer surface slidably mounted for reciprocating movement within said housing having its bottom end adjacent said base and its opposite top end extending outwardly from said housing for manual actuation thereof by movement toward said base into operative position and spring means normally maintaining said plunger in outwardly extended inoperative position, that improvement which consists of a removable housing base means for mounting said switch alternatively in one of two differently inclined positions, said removable housing base means comprising a receptacle element including a pair Of axially extended terminal elements mounted on said base and extending upwardly away therefrom for operation by said plunger, said receptacle element having positioning means inclined at a predetermined angle relatively to a plane perpendicular to said axis, and a housing base element, including a pair of terminals, having cooperating positioning means inclined at said predetermined angle, said base element cooperative positioning means comprising an attaching element and at least two orientation elements, and said receptacle positioning means comprising attachment element retaining means and at least two orientation element receiving means, said orientation element receiving means being adapted to receive said orientation elements in either of said differently inclined positions, thereby providing alternative inclination of said housing relatively to said receptacle element up to twice said predetermined angle, said terminals of said receptacle and housing base elements being in contact in said alternative inclinations, and an axially extended groove in said plunger having sides and a bottom-actuating surface including a rest surface extending for a substantial distance from said bottom end, said rest surface having a sloped end tapering inwardly toward said bottom end, and a cam surface sloping contiguously from the end of said rest surface remote from said bottom end toward said outer surface at an acute angle to the axis of said plunger, said plunger having a downwardly tapering conical outer surface at said bottom end, and having a stop within said housing, said housing having an overlying cooperating stop limiting outward displacement of said plunger when biased by said spring means, said axially extended terminal elements comprising an inner terminal element positioned within said groove in operative position of said plunger and having its remote end portion in contact with the bottom of said groove and an outer terminal element positioned outside of said groove and extending thereacross positively to maintain it out of contact with said inner terminal in inoperative position of said plunger, said inner terminal sliding upwardly past said sloped end of said rest surface, and said outer terminal sliding upwardly past said conical outer surface upon introduction of said removable base means into assembled position, whereby movement of said plunger toward said base moves said inner terminal by contact of its remote end portion with said groove cam surface relatively to said outer terminal. 